// -*- mode: c++; c-indent-level: 4; c++-member-init-indent: 8; comment-column: 35; -*-

//-----------------------------------------------------------------------------
// moeoFastNonDominatedSortingFitnessAssignment.h
// (c) OPAC Team (LIFL), Dolphin Project (INRIA), 2007
/*
    This library...

    Contact: paradiseo-help@lists.gforge.inria.fr, http://paradiseo.gforge.inria.fr
 */
//-----------------------------------------------------------------------------

#ifndef MOEOFASTNONDOMINATEDSORTINGFITNESSASSIGNMENT_H_
#define MOEOFASTNONDOMINATEDSORTINGFITNESSASSIGNMENT_H_

#include <eoPop.h>
#include <moeoComparator.h>
#include <moeoFitnessAssignment.h>
#include <moeoObjectiveVectorComparator.h>

/**
 * Fitness assignment sheme based on Pareto-dominance count proposed in: 
 * N. Srinivas, K. Deb, "Multiobjective Optimization Using Nondominated Sorting in Genetic Algorithms", Evolutionary Computation vol. 2, no. 3, pp. 221-248 (1994)
 * and in:
 * K. Deb, A. Pratap, S. Agarwal, T. Meyarivan, "A Fast and Elitist Multi-Objective Genetic Algorithm: NSGA-II", IEEE Transactions on Evolutionary Computation, vol. 6, no. 2 (2002).
 * This strategy is, for instance, used in NSGA and NSGA-II.
 */
template < class MOEOT >
class moeoFastNonDominatedSortingFitnessAssignment : public moeoParetoBasedFitnessAssignment < MOEOT >
{
public:

	/**
	 * Ctor
	 */
	moeoFastNonDominatedSortingFitnessAssignment() {}
	
	
	/**
	 * Computes fitness values for every solution contained in the population _pop
	 * @param _pop the population
	 */
	void operator()(eoPop < MOEOT > & _pop)
	{
		// number of objectives for the problem under consideration
		unsigned nObjectives = MOEOT::ObjectiveVector::nObjectives();
		if (nObjectives == 1)
		{
			// one objective
			oneObjective(_pop);
		}
		else if (nObjectives == 2)
		{
			// two objectives (the two objectives function is still to implement)
			mObjectives(_pop);
		}
		else if (nObjectives > 2)
		{
			// more than two objectives
			mObjectives(_pop);
		}
		else
		{
			// problem with the number of objectives
			throw std::runtime_error("Problem with the number of objectives in moeoFastNonDominatedSortingFitnessAssignment");
		}
	}


private:

	/** the objective vector type of the solutions */
	typedef typename MOEOT::ObjectiveVector ObjectiveVector;
	/** Functor to compare two objective vectors according to Pareto dominance relation */
	moeoParetoObjectiveVectorComparator < ObjectiveVector > comparator;
	/** Functor to compare two solutions on the first objective, then on the second, and so on */
	moeoObjectiveComparator < MOEOT > objComparator;
	
	
	/**
	 * Sets the fitness values for mono-objective problems
	 * @param _pop the population
	 */
	void oneObjective (eoPop < MOEOT > & _pop)
	{
		std::sort(_pop.begin(), _pop.end(), objComparator);
		for (unsigned i=0; i<_pop.size(); i++)
		{
			_pop[i].fitness(i+1);
		}
	}
	
	
	/**
	 * Sets the fitness values for bi-objective problems with a complexity of O(n log n), where n stands for the population size
	 * @param _pop the population
	 */
	void twoObjectives (eoPop < MOEOT > & _pop)
	{
		//... TO DO !
	}
	
	
	/**
	 * Sets the fitness values for problems with more than two objectives with a complexity of O(n² log n), where n stands for the population size
	 * @param _pop the population
	 */
	void mObjectives (eoPop < MOEOT > & _pop)
	{
		// S[i] = indexes of the individuals dominated by _pop[i]
		std::vector < std::vector<unsigned> > S(_pop.size());
		// n[i] = number of individuals that dominate the individual _pop[i]
		std::vector < unsigned > n(_pop.size(), 0);
		// fronts: F[i] = indexes of the individuals contained in the ith front
		std::vector < std::vector<unsigned> > F(_pop.size()+1);
		// used to store the number of the first front
		F[1].reserve(_pop.size());
		for (unsigned p=0; p<_pop.size(); p++)
		{
			for (unsigned q=0; q<_pop.size(); q++)
			{
				// if p dominates q
				if ( comparator(_pop[p].objectiveVector(), _pop[q].objectiveVector()) )
				{
					// add q to the set of solutions dominated by p
					S[p].push_back(q);
				}
				// if q dominates p
				else if  ( comparator(_pop[q].objectiveVector(), _pop[p].objectiveVector()) )
				{
					// increment the domination counter of p
					n[p]++;
				}
			}
			// if no individual dominates p
			if (n[p] == 0)
			{
				// p belongs to the first front
				_pop[p].fitness(1);
				F[1].push_back(p);
			}
		}
		// front counter
		unsigned counter=1;
		unsigned p,q;
		while (! F[counter].empty())
		{
			// used to store the number of the next front
			F[counter+1].reserve(_pop.size());
			for (unsigned i=0; i<F[counter].size(); i++)
			{
				p = F[counter][i];
				for (unsigned j=0; j<S[p].size(); j++)
				{
					q = S[p][j];
					n[q]--;
					// if no individual dominates q anymore
					if (n[q] == 0)
					{
						// q belongs to the next front
						_pop[q].fitness(counter+1);
						F[counter+1].push_back(q);
					}
				}
			}
			counter++;
		}
	}

};

#endif /*MOEOFASTNONDOMINATEDSORTINGFITNESSASSIGNMENT_H_*/